1. Field of the Invention
The invention relates to a pump for a hand actuated device for producing an atomized spray.
2. Description of the Prior Art
French patent No. 76 05718 describes such a pump, designed in such a manner that minimum pressure is applied to a piston before initiating atomization. It is contemplated that such to avoid undesirable atomization when the pressure is not sufficient. In view of this result, the pump described in this patent comprises a cylinder having an end wall with a valve therein, a piston slidable in the cylinder, a hollow stem with a lateral opening at one end, being slidable in and extending through the piston and extending outside the cylinder at the opposite end thereof to the valve and having actuating means thereon, the piston having a gasket for covering and uncovering the lateral opening in the stem as the stem moves relative to the piston, and wherein the piston is biassed in opposite directions by two spring means, one of the spring means biassing the piston away from the cylinder end wall with the valve, and being weaker than the other spring means, said other spring means being positioned between the piston and a step on the hollow stem, and being in a relaxed state when the pump is not in use.
When the pressure is applied on the stem, there is provided a movement of the piston relative to the stem. This movement has two effects:
(1) it uncovers the lateral opening in the stem allowing the compressed fluid to escape towards an atomization nozzle, this opening being normally closed by the gasket of the piston when the pump is not in use;
(2) the stronger spring means between the piston and the step on the hollow stem is set in compression under a load corresponding to a minimum atomization pressure for the fluid.
The fluid can be moved to the nozzle and discharged outwardly only if the opening in the stem is uncovered by the piston, and accordingly, only if the spring is compressed. It is thus ensured that the fluid can be discharged only with a minimum pressure, corresponding to the compression of the spring means resulting from the shifting of the piston, necessary for uncovering of the discharge opening. This opening can remain open only if the pressure is maintained inside the valve. If pressure decreases, the spring means pushes the piston on the stem and the opening is closed, i.e. the atomization is stopped. Then, the fluid cannot be discharged with a pressure lower than a predetermined pressure.
If the fluid were expelled directly through finger pressure on the stem, it would be possible, if the pressure is not strong enough to cause undesirable atomization, to have formation of droplets, or even causing fluid to pour along the container.
Applicant has noted that, for a good operation of such a device, it is necessary that the discharge opening be perfectly closed as long as the pressure has not reached the prescribed value.
The quality of tightness is then of great importance. There is known a number of means, products, packings and other devices for securing every desirable quality of tightness. Nevertheless, in the present case, a valve is provided for closing a container which is discarded when empty and consequently, the container with its valve form only a wrapping and the price of the assembly should not be substantially higher than the price of a wrapping. But the quality of the valve must be sufficient to ensure correct operation during the whole service life of the container, i.e. until it is empty. As a consequence, it is not possible to use good conventional solutions for tightness in view of the cost which is too high for the contemplated use.